I have a child (DS12) who had a 30+ difference between GAI and PSI on the only FSIQ for which we have scores (he recently had neuropsych eval, awaiting results). He has always tested well on state achievement, and seemed fairly remarkable in his "regular ed" classroom since very young age.
Our district handles gifted ed somewhat uniquely, I think, bc the program tests the children and doesn't assess the performance part--identification/service is based 100% on GAI (I think 133 is the current cut-off. My son is in 135-145 range, until PSI is included).
This works really well for the elementary program--gifted services are one day a week, in a standalone site, non-graded, exploratory, depth and complexity is the model.
As an aside: DS pretty much tanked in his first year of "rigor," in middle school--I think bc 2e stuff really began to matter. The MS program is essentially acceleration, amounted to a 1-2 year grade skip. He could handle the content but not the format. I suspect he'd have the same troubles at any MS, but that is conjecture.
My point: there is a lot of disparity when it comes to programs, services, delivery. If you place a child in an environment that is a good fit, it's likely the performance piece of IQ won't be a big deal, especially at such a young age. I encourage you to investigate the educational philosophy of the program you are considering.
